Control voltage generator for electrical fuel control system

ABSTRACT

A control voltage generator for receiving input signals representing the various operating conditions of a diesel engine, that is, the rotational speed of the engine and the degree of depression of an accelerator pedal etc., so as to generate control voltages corresponding to the fuel injection quantity characteristics required for the engine.

I United States Patent 1191 1111 3,731,664 T suzuki et al. 1 1 May 8,1973 [54] CONTROL VOLTAGE GENERATOR 3,407,793 10/1968 Lang ..123 32 EAFOR ELECTRICAL FUEL CONTROL 3,526,212 9 1970 Bassot ..123 119 R SYSTEM3,575,146 4/1971 Creighton ..123/32 EA a W r H 3,587,540 6/1971 Hofmannet al ..l23/l02 [75] Inventors: Yoshihiko Tsuzuki, Kariya; NobuhitoHobo, Inuyarna, both of Japan Primary Examiner-Laurence M. Goodridge r.-1 1 T 1 Attorney-Cushman, Darby & Cushman [73] Ass1gnee: NippondensoCo., Ltd., A1ch1-ken,

Japan [57] ABSTRACT [22] Filed: Mar. 10, 1971 A control voltagegenerator for receiving mput slgnals PP 122,661 representing the variousoperating conditions of a diesel engine, that is, the rotational speedof the en- 52 us. (:1 ..123/102 123/119 R 307/265 gine and the degreedepress acceleram 51 1111. c1 .rozm 51/00 Pedal m9 as generate whages[58] Field of Search ..123/32 EA 119 R responding the fuel inl'ectimquantity charac- 5 teristics required for the engine.

1 Claim, 9 Drawing Figures [56] References Cited UNITED STATES PATENTS3,425,401 2/1969 Lang ..l23/32 EA V5 FVG PVG AVG

PATENTEU SHEET 1 0F 2 Ava PVG

20 frfiFa/wA/vce" CURVE 0F F 1 6.

PERFORMANCE CURVE 1/ 0F Pl/G.

V9 PERFORMANCE CURVE [47 0F L5. 2 1 0 I V5 PERFORMANCE CURVE 0F AVG.

V 2e 6 s PERFORMANCE CURVE OF US INVENTORE) CONTROL VOLTAGE GENERATORFOR ELECTRICAL FUEL CONTROL SYSTEM The present invention relatesgenerally to an electrical fuel control system for a diesel engine, andmore particularly, to a control voltage generator for the fuel controlsystem which generates control voltages corresponding to the operatingconditions of the engine. The control voltages are employed to vary theamount of fuel injection to suit the requirements of the engine, thatis, to perform the so-called fuel metering.

The object of the present invention is therefore to provide a controlvoltage generator which generates control voltages corresponding to thefuel injection quantity characteristics required for a diesel enginewhen it receives input signals representing the various operatingconditions of the engine, such as, the engine speed and the degree ofdepression of the accelerator pedal. The control voltage generated bythe control voltage generator corresponds to the amount of fueldelivered for a single injection into each cylinder under differentoperating conditions of the engine. A system exemplary of a type ofengine fuel control system is described in Hobb et al. U.S. Pat. No.3,685,526. This control voltage is employed to control a mono-stabletimer circuit which is capable of controlling the width of a time pulseby the control voltage, whereby an electrical fuel control system isrealized in which the time pulse of the timer circuit is applied to asolenoid valve to control its valve opening duration so that the fuelquantity to be delivered for each injection by the solenoid valve isdetermined and the fuel thus delivered is injected into a cylinder ofthe engine.

According to the control voltage generator of the present invention,control voltages which meet the following operating requirements of theengine can be provided:

1. When starting the engine, an increasing fuel delivery characteristicis ensured,

2. The engine idling speed can be maintained at a constant value,

3. Under the full load conditions, the volume of injection correspondingto the full load conditions can be supplied at any given engine speedslower than the maximum speed of the engine,

4. Under the partial load conditions of the engine, the engine speed canbe set to any given value between the idling speed and the maximum speedso that a characteristic is satisfied according to which the volume ofinjection is varied to a suitable value between the volume of injectioncorresponding to the full load condition and the minimum volume tocompensate for any deviation of the engine speed from the set value, and

5. At higher engine speeds exceeding the maximum engine speed, thevolume of injection is maintained at the minimum volume of injectionwhich is almost a zero quantity.

In order to generate control voltages which meet the operatingrequirements of the engine described above, the control voltagegenerator according to the present invention comprises a start andidling control voltage generating circuit which receives, as its inputsignal, a voltage substantially proportional to the engine speed, i.e.,the speed voltage, a full load control voltage generating circuit forgenerating a control voltage for the full load operation, and a partialload control voltage generating circuit which receives, as its inputsignal in addition to the speed voltage, a voltage as determined inaccordance with the degree of depression of the accelerator pedal, i.e.,the set voltage to generate a control voltage for the partial loadoperation, whereby of those control voltages which are generated by thethree control voltage generating circuits, the full load control voltageand the partial load control voltage are introduced into a lowerselector circuit which selects the lower limiting value of the twoapplied voltages, and the lower limiting value is then introduced intoan upper selector circuit along with the start and idling controlvoltage so that the upper selector circuit selects the upper limitingvalue of the two applied voltages to thereby produce an overall controlvoltage. Thus, it is possible to generate control voltages which meetall the operating requirements of the engine under starting, idling,full load and partial load conditions.

The above and other objects and features of the present invention willbecome readily apparent from the following descriptions of the preferredembodiments of the invention taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a block diagram showing the general construction ofthe control voltage generator according to the present invention;

FIGS. 2a to 2e show the input and output waveforms of the respectivecontrol voltage generating circuits incorporated in the control voltagegenerator shown in FIG. 1;

FIG. 3 is an electrical wiring diagram showing an embodiment of thecontrol voltage generator of the present invention;

FIG. 4 is a diagram showing the output voltage characteristics of thecontrol voltage generator according to the present invention; and

FIG. 5 is an output characteristic diagram of another embodiment of thecontrol voltage generator according to the present invention.

The general construction of the device of the present invention will nowbe explained with reference to FIG. 1. In this figure, numeral 1designates a full load control voltage generating circuit; 2 a partialload control voltage generating circuit; 3 a lower selector circuit; 4 astart and idling control voltage generating circuit; 5 an upper selectorcircuit. The full load control voltage generating circuit 1 receives, asits input signal, a voltage substantially proportional to the enginespeed, that is, a speed voltage V to generate a control voltage V; shownin FIG. 2a which corresponds to the amount of fuel injection requiredfor the full load operation of the engine. When the speed voltage V Vthe control voltage V,- changes to the minimum voltage V correspondingto the minimum amount of fuel injection.

The partial load control voltage generating circuit 2 generates apartial load control voltage V; shown in FIG. 2b, which is determined bytwo input signals including the speed voltage V and a voltage which isset according to the engine accelerator pedal movement 0, that is, a setvoltage V This partial load control voltage V is a control voltagecorresponding to the amount of fuel injection required for the partialload operation of the engine.

The lower selector circuit 3 is designed such that when a plurality ofinput voltages are applied thereto,

the circuit selects as its output voltage the minimal input signalvoltage from among the applied input voltages. Thus, when the full loadcontrol voltage V and the partial load control voltage V are applied tothe selection circuit 3 as its inputs, the smaller one of the twocontrol voltages applied is selected as its output voltage V as shown inFIG. 2c. The start and idling control voltage generating circuit 4receives the speed voltage V as its input signal and produces a controlvoltage V,, shown in FIG. 2d, which corresponds to the amount of fuelinjection required for the engine at speeds ranging from its start tothe idling speed.

The upper selector circuit is a circuit which when a plurality of inputvoltages are applied thereto, selects the largest input voltage fromamong the applied input voltages. In operation, the start and idlingcontrol voltage V and the output voltage V of the lower selector circuit3 are applied to the selection circuit 5; as its inputs, so that thelarger one of the two control voltages applied is selected as an overallcontrol voltage V,;. This situation is shown in FIG. 2e.

In this way, the overall control voltage V as generated by the upperselector circuit 5 is a control voltage corresponding to the amount offuel injection required for the engine under all the operatingconditions including the starting and idling as well as the partial loadand full load conditions.

Next, an embodiment of the control voltage generator according to thepresent invention will now be explained with reference to the electricalwiring diagram shown in FIG. 3. In this figure, numeral 1 designates thefull load control voltage generating circuit; 2 the partial load controlvoltage generating circuit; 3 the lower selector circuit; 4 the startand idling control voltage generating circuit; 5 the upper selectorcircuit, 6 a constant DC voltage source.

Of these essential units, the control voltage generating circuits 1, 2and 3 are circuits which are practically similar in construction andfunction and therefore the construction and function of the full loadcontrol voltage generating circuit 1 will be explained in detail by wayof an example. In the full load control voltage generating circuit 1,numeral 21 designates a transistor; 22 a reference diode; 23 a speedvoltage source for generating a DC voltage substantially proportional tothe speed of the engine; 24, 25 and 26 potentiometers; 27, 28, 29, 30and 31 resistors. In this construction, the speed voltage source 23 maybe comprised of a DC generator operatively associated with the enginecrankshaft, for example. Referring to FIG. 3, the sum voltage of avoltage across a voltage dividing point d of the voltage source 6 by thepotentiometer 2, i.e., a set voltage V and a voltage across the voltagedividing points a and d of the speed voltage V by the potentiometer 26,is applied between the point a at one end of the reference diode 22 anda grounding point e. Consequently, when the speed voltage V is lowerthan a predetermined value V the voltage between the points a and ecannot exceed the breakdown voltage of the reference diode 22 (strictly,a voltage higher than the breakdown voltage by a value corresponding tothe threshold voltage between the base and the emitter of the transistor2!) and no biasing voltage is applied to the base of the transistor 21in the forward direction so that the transistor 21 is cut off and hencethe voltage between its collector point c and the grounding point ebecomes substantially equal to a voltage V between a voltage dividingpoint g of the voltage source 16 by the potentiometer 24 and thegrounding point e. As the speed voltage V rises so that it becomeshigher than the speed voltage V the reference diode 22 is renderedconductive by the voltage between the points and e and a bias voltage isapplied to the base of the transistor 21 in the forward direction thusconducting the transistor 21, whereupon the voltage between thecollector point 0 of the transistor 21 and the grounding point egradually decreases as the speed voltage V continues to rise. Then, whenthe speed voltage V V (V 1 V a full conduction level is attained betweenthe collector and the base of the transistor 21 and hence the voltagebetween the points c and e assumes a fixed value, i.e., the minimumvalue V The value of V is determined to correspond to the amount of fuelinjection required for the engine at the full load and the value of V isdetermined to correspond to the minimum amount of fuel injection, whilethose of V and V 1 are determined to correspond to the engine speed atthe maximum output power and the maximum allowable engine speed,respectively. This operation is shown in FIG. 2a. The other controlvoltage generating circuits 1, 2 and 3 are practically the same with thefull load control voltage generating circuit 1 in construction andfunction, and therefore they will not be explained in detail but inbrief. The start and idling control voltage generating circuit 3generates the starting control voltage V V, when the speed voltage V Vand when V V V 2 the control voltage gradually decreases from V, to V asthe speed voltage V increases so that when V 5 V V V 1 (the minimumvalue). The values of V, and V 1 are determined to correspond to theamounts of fuel injection required for the engine starting and idling,respectively, while the values of V and V 2 are determined to correspondto the engine starting speed and idling speed, respectively. The partialload control voltage generating circuit 2 may be constructed such thatits potentiometer 41 varies in association with the movement of theengine accelerator pedal, and in this way the voltage between points fand e, that is, the set voltage can be adjusted as desired in accordancewith the movement 6 of the accelerator pedal. Correspondingly, the pointwhere the control voltage V starts to decrease from the maximum value Vcan be set as desired. If it is set that 0 0,, then V V when V V andwhen V 5 V V the value of V gradually decreases from V to V as the valueof V increases and it reaches the minimum value V when V V With thecondition 0 0 0 (where 0 0 indicates the minimum movement of theaccelerator pedal and 0,, is the full movement of the acceleratorpedal), the value of the speed voltage V at which the value of V startsto decrease from V can be set as desired. Consequently, any givencontrol voltage corresponding to the engine operating conditions at thepart load can be generated.

Next, the lower selector circuit 3 will be explained. The basic form ofthe lower selector circuit 3 for two input voltages comprises diodes 43and 44 and a resistor 45a and in this embodiment an emitter followercircuit comprising a transistor 45 is also combined for currentamplification of the selected output of the circuit. Numeral 46designates a resistor. The full load control voltage V and the partialload control voltage V are applied to the diodes 43 and 44,respectively, so that the smaller one of the full load control voltageV,- and the partial load control voltage V is selected to appear betweena junction point k of the diodes 43 and 44 and the resistor 45a and agrounding point e. Here, the value of the forward voltage drop of eitherthe diode 43 or 44 is so small that it is neglected. The output voltageV of the lower selector circuit 3 appears between points m and e afterits current amplification by the emitter follower transistor 45.

Next, the upper selector circuit 5 will be explained. The ba'sic form ofthe upper selector circuit 5 for receiving two input voltages comprisesdiodes 47 and 48 and a resistor 49 and in this embodiment the selectorcircuit 5 is also combined with an emitter follower circuit comprising atransistor 48a for current amplification of its selected output. Numeral51 designates a resistor, 52 a capacitor provided for filteringpurposes. The output voltage V of the lower selector circuit 3 and thestart and idling control voltage V, are applied to the diodes 47 and 48,respectively, so that the larger one of the two voltages V and V isselected and developed between a junction point n of the diodes 47 and48 and the resistor 49 and a grounding point e. Here, the value of theforward voltage drop of the diode 47 or 48 is neglected. The outputvoltage of the upper selector circuit 5 is supplied to the emitterfollower transistor 48a for current amplification so that the overallcontrol voltage V is produced between points p and e.

With the circuit construction described above, the overall controlvoltage V produced between the points p and e can satisfy all theoperating requirements of a diesel engine under starting, idling, fullloading and partial load conditions as shown in FIG. 4 (where theabscissa represents the speed voltage V and the ordinate represents theoverall control voltage V In FIG. 4, the reference characters areidentical with those which are used in the foregoing explanation. inpractice, when the engine is started with the accelerator pedal movement0 0, the value of the speed voltage V is determined according to thespeed of the engine so that the value of the corresponding controlvoltage V is determined along the line drawn through points A, B, C andD on the graph. On the other hand, if the accelerator pedal movement 0 0(the maximum), then the control voltage V corresponding to the speedvoltage V is similarly determined along the line drawn through thepoints A, B, G and H. Similarly, if the value of the accelerator pedalmovement 0, is 0 0, 0 then the control voltage V is determined along theline drawn through the points A, B, C, E and F according to the speedvoltage V In this way, the characteristics shown in FIG. 4 represent thecontrol voltage characteristics which have practically the same formwith that of the fuel quantity controlling characteristics by theso-called all-speed governor for a diesel engine.

hile both the full load control voltage generating circuit 1 and thestart and idling control voltage generating circuit 4 have beendescribed in the form of circuits adapted to provide the mostfundamental control voltage characteristics, these control voltagegenerating circuits may comprise, for example, analogicalfunctiongenerators which provide any functional relations. Therefore, byemploying control voltage generating circuits which are capable ofproviding, as shown in FIG. 5, the curve l-J-K-L-M as the controlvoltage characteristic of the start and idling control voltagegenerating circuit and the curve K-N-O-P-Q as the control voltagecharacteristic of the full load control voltage generating circuit,control voltages which more precisely suit the operating conditions ofan engine may be generated.

What is claimed is:

1. A control voltage generator for an electrical fuel control systemused with pulse generating means for generating pulses, and fuelinjection solenoid valves controlled by the pulses generated by saidpulse generating means, said control voltage generator comprising:

first means for generating a voltage representative of an actual enginespeed,

a first circuit electrically connected to said first means forgenerating a voltage corresponding to the amount of fuel injectionrequired for the full load operation of the engine at said actual enginespeed,

second means for generating a voltage representative of an actual engineload,

a second circuit electrically connected to said first and second meansfor generating a voltage corresponding to the amount of fuel injectionrequired for the engine at said actual engine load and said actualengine speed,

a third circuit electrically connected to said first means forgenerating a voltage which varies from a value corresponding to theamount of fuel injection for the engine at starting where said actual engine speed is below a predetermined first speed and to another valuecorresponding to the amount of fuel injection for the engine at idlingwhere said actual engine speed is higher than a predetermined secondspeed,

a lower selector circuit electrically connected to said first and secondcircuits for selecting a smaller one of said voltages generated by saidfirst and second circuits and permitting said smaller voltage to beapplied to an upper selector circuit, and

said upper selector circuit electrically connected to said lowerselector circuit and said third circuit for selecting a larger one ofsaid smaller voltage derived from said lower selector circuit and saidvoltage generated by said third circuit, said larger voltage beingadaptable to be utilized for controlling the widths of the pulsesproduced by the pulse generating means.

l F i l t UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,731,66Dated May 8, 1973 Patent No.

Inventor(s) Yoshihiko Tsuzuki and Nobuhito Hobo It' is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

11 the headigg:

Item [30] Foreign Application Priority Data March 12, 1970 Japan.2lO33/7O Signed and sealed this 27th day ofNovember 1973.

(SEAL) Attest;

EDWARD M.FLETCHER,JR. RENE 1). TEGTMEYER Attesting Officer AqtingCommissioner of Patents USCOMM'DC 6Q376-F'69 9 U.S GOVERNMENT PRINTINGOFFICE: I96! 0-366-334 F ORM FO-IOSO (10-69)

1. A control voltage generator for an electrical fuel control system used with pulse generating means for generating pulses, and fuel injection solenoid valves controlled by the pulses generated by said pulse generating means, said control voltage generator comprising: first means for generating a voltage representative of an actual engine speed, a first circuit electrically connected to said first means for generating a voltage corresponding to the amount of fuel injection required for the full load operation of the engine at said actual engine speed, second means for generating a voltage representative of an actual engine load, a second circuit electrically connected to said first and second means for generating a voltage corresponding to the amount of fuel injection required for the engine at said actual engine load and said actual engine speed, a third circuit electrically connected to said first means for generating a voltage which varies from a value corresponding to the amount of fuel injection for the engine at starting where said actual engine speed is below a predetermined first speed and to another value corresponding to the amount of fuel injection for the engine at idling where said actual engine speed is higher than a predetermined second speed, a lower selector circuit electrically connected to said first and second circuits for selecting a smaller one of said voltages generated by said first and second circuits and permitting said smaller voltage to be applied to an upper selector circuit, and said upper selector circuit electrically connected to said lower selector circuit and said third circuit for selecting a larger one of said smaller voltage derived from said lower selector circuit and said voltage generated by said third circuit, said larger voltage being adaptable to be utilized for controlling the widths of the pulses produced by the pulse generating means. 